Use Compartment.p.evaluate instead of eight magic lines

Currently, even on xsnap, we’re building SES essentially the same way we do on normal JS, by running the full SES shim including the eight magic lines built on direct eval. Currently, XS eval does not understand the sourceURL directive, so all SES code runs in XS without any tie to a filename. Also, using the eight magic lines, we cannot fix #31

Instead, we could switch to using the XS builtin Compartment.prototype.evaluate as our safe evaluator, replacing the eight magic lines, while still building the rest of SES using code from the SES shim. This should immediately fix #31 .

In addition, perhaps it is easier to get XS to accept a filename via Compartment.prototype.evaluate rather than the sourceURL directive in an eval? Attn @phoddie

[kriskowal]

We’ll need a follow-up change in SES to feature-detect the suitable XS Compartment and switch the behavior of performEval to use that instead of the “three wrongs of with + sloppy + eval that make a right”.

[erights]

For the “sloppy globals” issue, we could painlessly add a dirt simple translator to our repl, replacing a first line matching

/^(\s*)(\w*\s*=)/

with

`${m[1]}globalThis.${m[2])`